The invention relates to fuel injectors, and more particularly to a holder body for a fuel injection valve for internal combustion engines.
One known holder body, disclosed in European Patent Disclosure EP 0 569 727, has a cylindrical basic shape, and a central axial blind bore is machined into its end face oriented toward the combustion chamber This blind bore, extending approximately as far as an axially middle region of the holder body, serves in the holder body of the fuel injection valve to receive a valve spring, which urges a valve member of the fuel injection valve in the closing direction. A fuel flow conduit is also provided in the holder body; it is formed of an axial blind bore originating at the end face toward the combustion chamber and a radial bore intersecting it; the radial bore emerges laterally at a cylindrical jacket face of the holder body. The bore intersection between the axial bore of the flow conduit and the preferably obliquely disposed radial bore is provided in a region axially downstream of the closed end of the blind bore that receives the valve spring. The lateral outlet opening of the flow conduit on the circumferential wall of the holder body has a conical seat face, at which a pressure tube neck comes to rest with its conical end face; this pressure tube neck is braced radially against the holder body via lock nuts. The known holder body with a lateral pressure tube connection has the disadvantage that as a consequence of the lateral bracing of the pressure tube neck against the holder body, radial forces are introduced to the holder body that impair its durability. A sharp deflection of the fuel stream also occurs at the bore intersection between the bore segments of the flow conduit, and this has a deleterious effect on the fuel flow in the flow conduit. A further disadvantage of the bore intersection of the partial bores of the flow conduit is caused by the notch effect that occurs there, which can reduce the durability of the holder body still further. Furthermore, the known holder body with a lateral pressure tube connection has the disadvantage that it is relatively complicated to produce and to install, so that its realization requires high production effort and expense.
The holder body of the invention for a fuel injection valve for internal combustion engines has the advantage over the prior art that a lateral connection of a high-pressure fuel delivery line on the holder body is possible without thereby introducing radial forces to the holder body and without an unstreamlined bore intersection inside the holder body. This is advantageously possible by kinking or angling the holder body. In this way, a laterally incoming high-pressure line can be screwed in a structurally simple way to the end of the holder body remote from the combustion chamber, and known high-pressure connection necks can be used. The fuel inflow opening in the holder body is provided in the end face of the holder body remote from the combustion chamber, and only after the through bore forming the flow conduit is made in the holder body is the holder body bent to the final amount. In this way, bore intersections that occur when an oblique bore intersects a straight bore can be avoided. A further advantage, besides the avoidance of radial fastening forces and bore intersections in the flow conduit, is the use of conventional pressure tube necks screwed onto the holder body, so that the additional fastening crossbars can be dispensed with. With the provision of the unilateral lateral recess on the circumferential face of the holder body, a greater bending angle can also be attained when the holder body is bent; this angle can be up to 90xc2x0 and more. The holder body can be manufactured in a simple way, and various courses of production are possible. The holder body can initially be embodied like a known holder body, into which, after the spring chamber blind bore and the flow conduit have been made, the lateral recess is machined, and which is then angled accordingly on a bending bench. However, it is also possible to prepare a holder body blank in which the lateral recess is already provided. This blank can be produced with the recess without metal cutting, for instance by forging, rolling, stamping and the like; however, the recess can also be made by metal-cutting methods, such as milling, or on a lathe, in a cylindrical holder body blank. After that, the appropriate bores are then made in the holder body, and a partial region of the flow conduit that receives a fuel filter is advantageously made, beginning at the end face remote from the combustion chamber, in the form of an oblique bore with a slight angle of inclination to the longitudinal axis of the holder body and then in a known manner discharges into an axial longitudinal bore offset laterally from the spring chamber. In this case as well, the angling of the holder body by a predetermined angle is done as a final work step, preferably on a bending bench. The angled region of the holder body is provided in the region of the lateral cross-sectional recess on the holder body, and the holder body is always angled in the direction remote from the lateral recess. Alternatively, other production methods are possible, for instance in which the flow conduit is embodied as a straight-line through bore, to which end the holder body, in the region outside the spring chamber, is bent slightly out of the center axis of the spring chamber, so that the through bore offset from the spring chamber can discharge into the end face, remote from the combustion chamber, of the holder body. It is advantageous, at the outlet opening of the flow conduit on the end face remote from the combustion chamber, to provide a conical bore outlet; these conical faces form a bearing face for a pressure tube connection to be screwed on. A further advantageous exemplary embodiment of the production method for the holder body of the invention is attained by combining the aforementioned method steps; first, the axial central blind bore forming the spring chamber is made in the holder body from the lower end face, nearer the combustion chamber. At the same time, on the opposite end face of the holder body remote from the combustion chamber, a central blind bore can be made that in terms of its cross section is dimensioned so as to be suitable for receiving a rod filter. In a further work step, the holder body is then angled slightly in the region outside the spring chamber, so that now an axial blind bore offset laterally from the spring chamber can be made in the holder body in such a way that it discharges into the blind bore region intended for receiving the bar filter. In this case as well, the lateral machining of a recess on the circumference of the holder body and following that the bending of the holder body in the direction remote from the lateral recess are now done. Beyond the four examples of methods shown in the description, it is furthermore possible to produce the holder body of the invention by combining the various method steps known from these four examples with one another. What is essential is that the bore geometry of the flow conduit and preferably also of the spring chamber in the holder body be established before the holder body is angled into its final form.
Thus with the holder body of the invention for a fuel injection valve for internal combustion engines, it is possible to furnish a lateral high-pressure connection that in a structurally simple way overcomes the disadvantages of an induction of force radially to the holder body and of a bore intersection inside the holder body, and onto which high-pressure pressure connection the known pressure tube neck can be screwed axially onto the end remote from the combustion chamber in a simple way. This holder body for receiving laterally incoming high-pressure fuel lines can be produced in an especially simple and economical way by using the production methods described.